A vehicle developed into a vehicular communication system that not only is transportation but can also provide services such as real-time traffic information, digital map, movie and music through external internet. A Vehicular Ad-hoc Network (hereinafter, referred to as “VANET”) technology including the aforementioned vehicular communication system should be suitable for fast speed and frequent mobility of a vehicle hence, network technology that is different from the related art of Mobile Ad-hoc Network (hereinafter, referred to as “MANET”) is required.
IEEE WAVE (Wireless Access in Vehicular Environment) is a wireless communication standard to provide the above VANET service including IEEE 802.11p and IEEE 1609 standard. Additionally, the IEEE WAVE supports fast link connection between OBU (On-Board Unit) for a vehicle driving in a maximum speed of 160 km/h and RSU (Road-Side Unit) installed in road-sides and high speed data transmission of maximum 27 Mbps. Technology regarding IEEE WAVE standard have been developing mainly in the North American region and active commercialization and standardization is being promoted also in Europe, Japan and etc. Moreover, the Ministry of Land of the Republic of Korea is promoting IEEE WAVE standard technology as a candidate technology.
A service provider of the Road-Side Unit (hereinafter, referred to as “RSU”) and etc. periodically transmits Wave Service Advertisement (hereinafter, referred to as “WSA”) with network parameter such as WBSS recognizor, a service channel used by a WBSS, timing information for synchronization that is necessary to register for WBSS (Wave BSS) as a method to provide services through the IEEE 802.11p standard WAVE mode. Herein, the WSA message receiving vehicle communication device may receive related service using service channel information and etc. included in the WSA message thereof.
However, there is a problem that a vehicular communication device that did not receive the WSA message from the service provider of the RSU unit and etc. may have to wait to receive the WSA message until next transmission period to receive related services.
In the paper Augmenting Vehicle-to-Roadside connectivity in multi-channel vehicular Ad Hoc Networks by C. Campolo et el. suggests a method of receiving WSA message through other vehicular communication device. In the paper, when the vehicular communication device receives a WSA message, the WSA message broadcasts the piggybacked beacon message to proximate vehicular communication device, thereby suggesting that vehicular communication device that did not receive the WSA message can receive the WSA message through the message.
However, when the entire vehicular communication device that received the WSA message broadcasts the piggybacked beacon message as the method suggested in the paper, total capacity of the beacon message increases, thereby causing overload of the related channel. Additionally, QoS service through WAVE mode may be degraded due to the channel overload.